The invention relates to an antistatic molded article comprising a polyesteramide resin, particularly a molded article comprising a resin prepared by copolymerizing a cyclic amide and a cyclic ester and/or a linear ester, and further a molded article comprising a polyesteramide resin prepared by reacting a chemical compound having at least two hydroxyl groups, together with the above monomers.
A molded resin article provided with an antistatic property is widely used in electric appliances and electronic instruments. Especially, this is used in various kinds of parts used in production lines of semiconductor-related products, such as carrier pallets, housings, bearings, guides, and rollers.
To provide an antistatic property to a polymer matrix, for example, thermoplastic resins, the following methods have been employed: to add an electrically conductive filler such as graphite, carbon black, carbon fibers, metal oxides, metal powder, and metal fibers; to add or apply an antistatic agent to the surface, such as a surface-active agent; or to add an electrically conductive polymer.
It is rather easy to decrease a surface conductivity by blending in an electrically conductive filler. However, the filler must be added usually in an amount of as much as about 20 wt % of the molded article, so that homogeneous dispersion is difficult. Further, there is a problem of high costs. When an electrically conductive carbon filler is used, a molded article gets black and therefore coloration is limited, and sometimes its application field may be limited because of contamination with carbon powder. Further, it is difficult to steadily attain a required resistivity range of an order of from 109 to 1012xcexa9. If the resistivity is lower than this, in IC related parts, circuits in the IC may be damaged.
In the case where a surface-active agent is added to the polymerization system, the surface-active agent may inhibit the reaction or decompose at a high mold temperature; and even when the required resistivity is attained, the resistivity may change with time or a problem of ion extraction may arise, which problem is fatal in semiconductor production lines. In the case where a surface-active agent is applied on a surface of a molded article, there are problems that heat resistance is poor; the antistatic property degrades with time; and the surface-active agent adversely affects circuits in IC related parts.
The use of an electrically conductive polymer is better in that there is not the problem of ion extraction. However, the polymer is very expensive, and the molding temperature may be a limiting factor, like in the case of the use of a surface-active agent.
The object of the present invention is to provide an antistatic molded article having a desired surface resistivity without using a substantive amount of an electrically conductive additive, which article can be obtained easily and economically.
To solve the above problems, the present inventor has had an idea of attaining using a substantive amount of an electrically conductive antistatic property only by molecular skeleton structure without using a substantive amount of an electrically conductive additive, and has completed the present invention.
Thus the present invention is an antistatic molded article comprising a polyesteramide resin, characterized in that said molded article is prepared by copolymerizing (a) a cyclic amide and at least one ester selected from the group consisting of (b1) a cyclic ester and (b2) at least one linear ester selected from the group consisting of polyesterpolyol, polyesteretherpolyol, and polycarbonatepolyol, said molded article having a surface resistivity of less than 1013xcexa9.
Preferred embodiments of the above antistatic molded article comprising a polyesteramide resin are as follows:
the antistatic molded article comprising a polyesteramide resin, wherein the surface resistivity is in a range of from 109 to 1012xcexa9;
the antistatic molded article comprising a polyesteramide resin, wherein said molded article is prepared by ring-opening copolymerizing the cyclic amide (a) and the cyclic ester (b1) in a weight ratio of (a) to (b1) of from 100:3 to 100:44;
the antistatic molded article comprising a polyesteramide resin, wherein said molded article is prepared by copolymerizing the cyclic amide (a) and the cyclic ester (b1) in a weight ratio of (a) to (b1) of from 100:3 to 100: less than 10, wherein an electrically conductive material is further provided;
the antistatic molded article comprising a polyesteramide resin, wherein said molded article is prepared by ring-opening copolymerizing the cyclic amide (a) and the cyclic ester (b1) in a weight ratio of (a) to (b1) of from 100:10 to 100:34;
the antistatic molded article comprising a polyesteramide resin, wherein said molded article is prepared by copolymerizing the cyclic amide (a) and the linear ester (b2), or a mixture of the linear ester (b2) and the cyclic ester (b1) in a weight ratio of (a) to (b2) or (a) to the mixture of (b2) and (b1) of from 100:2 to 100:50;
the antistatic molded article comprising a polyesteramide resin, wherein said molded article is prepared by copolymerizing the cyclic amide (a) and the linear ester (b2) or a mixture of the linear ester (b2) and the cyclic ester (b1), in a weight ratio of (a) to (b2) or (a) to the mixture of (b2) and (b1) of from 100:2 to 100: less than 5, wherein an electrically conductive material is further provided;
the antistatic molded article comprising a polyesteramide resin, wherein said molded article is prepared by copolymerizing the cyclic amide (a) and the linear ester (b2) or the mixture of the cyclic ester (b1) and the linear ester (b2), in a weight ratio of (a) to (b2) or (a) to the mixture of (b2) and (b1) of from 100:5 to 100:45;
the antistatic molded article comprising a polyesteramide resin, having a tensile strength, measured according to ASTM D-638, of at least 40 MPa;
the antistatic molded article comprising a polyesteramide resin, wherein the linear ester (b2) is polycaprolactonediol;
the antistatic molded article comprising a polyesteramide resin, wherein the cyclic ester (b1) is xcex5-caprolactone; and
the antistatic molded article comprising a polyesteramide resin, wherein the cyclic amide (a) is xcex5-caprolactam.
Further, the present invention relates to a polyesteramide resin prepared by reacting 100 parts by weight of (a) a cyclic amide, 5 to 50 parts by weight of (b2) at least one linear ester selected from the group consisting of polyesterpolyol, polyesteretherpolyol, and polycarbonatepolyol, or 5 to 50 parts by weight of a mixture of at least 5 parts by weight of the linear ester (b2) and (b1) a cyclic ester, and (c) a chemical compound having a molecular weight of 200 or smaller and having at least 2 hydroxyl groups, wherein said resin has a number average molecular weight, reduced from polystyrene, of from 4,000 to 100,000.
Preferred embodiments of the above polyesteramide resin are as follows:
the polyesteramide resin, wherein said polyesteramide resin has the surface resistivity of from 106 to 109xcexa9;
the polyesteramide resin, wherein said polyesteramide resin has a volume resistivity of from 104 to 107xcexa9.m.;
the polyesteramide resin, wherein the chemical compound (c) is used in such an amount that a molar ratio of the hydroxyl groups, defined by the following equation, is in a range of from 0.1 to 1.0, wherein the molar ratio of the hydroxyl groups=molar amount of the hydroxyl group of the chemical compound (c)/molar amount of the hydroxyl group of the linear ester (b2);
the polyesteramide resin, wherein the molar ratio of the hydroxyl groups is in the range of from 0.2 to 0.5;
the polyesteramide resin, wherein the chemical compound (c) has at least 3 hydroxyl groups;
the polyesteramide resin, wherein the chemical compound (c) is trimethylolethane, trimethylolpropane or a mixture of trimethylolethane and trimethylolpropane;
the polyesteramide resin, wherein the cyclic amide (a) is xcex5-caprolactam;
the polyesteramide resin, wherein the cyclic ester (b1) is xcex5-caprolactone;
the polyesteramide resin, wherein the linear ester (b2) is polycaprolactonediol; and
an antistatic molded article comprising the above mentioned polyesteramide resin.
Any one of the above-mentioned molded article is prepared preferably by a monomer casting method.
Further, the present invention is a method for preparing an antistatic polyesteramide resin by ring-opening copolymerizing (a) a cyclic amide and (b1) a cyclic ester in a weight ratio of from 100:3 to 100:44.
In the above method, it is preferred that the cyclic amide (a) and the cyclic ester (b1) are ring-opening copolymerized in a weight ratio of from 100:10 to 100:34.
Still further, the present invention is a method for preparing an antistatic polyesteramide resin by copolymerizing (a) a cyclic amide and (b2) at least one linear ester selected from the group consisting of polyesterpolyol, polyesteretherpolyol, and polycarbonatepolyol or a mixture of the linear ester (b2) and (b1) a cyclic ester, in a weight ratio of from 100:2 to 100:50.
In the above method, it is preferred that the cyclic amide (a) and the linear ester (b2) or the mixture of the linear ester (b2) and the cyclic ester (b1) are copolymerized in a weight ratio of from 100:5 to 100:45. It is also preferred that either the linear ester (b2) is polycaprolactonediol; that the cyclic ester (b1) is xcex5-caprolactone; and that the cyclic amide (a) is xcex5-caprolactam.
Further, the present invention is a method for preparing a polyesteramide resin by reacting 100 parts by weight of (a) a cyclic amide, 5 to 50 parts by weight of (b2) at least one linear ester selected from the group consisting of polyesterpolyol, polyesteretherpolyol, and polycarbonatepolyol, or 5 to 50 parts by weight of a mixture of (b2) at least 5 parts by weight of the linear ester and (b1) a cyclic ester, and (c) a chemical compound having a molecular weight of 200 or smaller and having at least 2 hydroxyl groups.
The preferred embodiments of the above method are as follows:
the method for preparing a polyesteramide resin, wherein the chemical compound (c) is reacted in such an amount that the molar ratio of the hydroxyl groups, defined by the following equation, is in the range of from 0.1 to 1.0, wherein the molar ratio of the hydroxyl groups=molar amount of the hydroxyl group of the chemical compound (c)/molar amount of the hydroxyl group of the linear ester (b2);
the method for preparing a polyesteramide resin, wherein the molar ratio of the hydroxyl group is in the range of from 0.2 to 0.5;
the method for preparing a polyesteramide resin, wherein the chemical compound (c) has at least 3 hydroxyl groups;
and the method for preparing a polyesteramide resin, wherein the chemical compound (c) is trimethylolethane, trimethylolpropane of a mixture of trimethylolethane and trimethylolpropane.
In any one of the above methods, it is preferred that either the cyclic amide (a) is xcex5-caprolactam; that the cyclic ester (b1) is xcex5-caprolactone; and that the linear ester (b2) is polycaprolactonediol.
It is preferred that a monomer casting method is used for the copolymerization in any one of the above-mentioned methods.
Further, the present invention is a method for making a polyesteramide resin antistatic, wherein the polyesteramide resin molded article is prepared by ring-opening copolymerizing (a) a cyclic amide and (b1) a cyclic ester, characterized in that the ratio of the cyclic amide (a) to the cyclic ester (b1) is set in a range of from 100:3 to 100:44.
In the above method, it is preferred that the ratio of the cyclic amide (a) to the cyclic ester (b1) is set in a range of from 100:10 to 100:34.
Still further, the present invention is a method for making a polyesteramide resin antistatic, wherein the polyesteramide resin is prepared by copolymerizing (a) a cyclic amide and (b2) at least one linear ester selected from the group consisting of polyesterpolyol, polyesteretherpolyol and polycarbonatepolyol or a mixture of the linear ester (b2) and (b1) a cyclic ester, characterized in that the weight ratio of the cyclic amide (a) to the linear ester (b2) or to the mixture of the cyclic ester (b1) and the linear ester (b2) is set in a range of from 100:2 to 100:50.
In the above method, it is preferred that the weight ratio of the cyclic amide (a) to the linear ester (b2) or the mixture of the cyclic ester (b1) and the linear ester (b2) is set in a range of from 100:5 to 100:45.
The present invention also relates to a method for making a polyesteramide resin antistatic, wherein the polyesteramide resin is prepared by copolymerizing (a) a cyclic amide and (b2) at least one linear ester selected from the group consisting of polyesterpolyol, polyesteretherpolyol or a mixture of the linear ester (b2) and (b1) a cyclic ester, characterized in that the weight ratio of the cyclic amide (a) to the linear ester (b2) is set in the range of from 100:5 to 100:50, or the weight ratio of the cyclic amide (a) to the mixture of the linear ester (b2) and the cyclic ester (b1) is set in the range of from 100:5 to 100:50, wherein the weight ratio of the linear ester (b2) to the cyclic amide (a) is at least 5:100, and (c) a chemical compound having a molecular weight of 200 or smaller and having at least 2 hydroxyl groups.
The preferred embodiments of the above method are as follows:
the method for making the polyesteramide resin antistatic, wherein the chemical compound (c) is added in such an amount that the molar ratio of the hydroxyl groups, defined by the following equation, is in the range of from 0.1 to 1.0, wherein the molar ratio of the hydroxyl groups=molar amount of the hydroxyl group of the chemical compound (c)/molar amount of the hydroxyl group of the linear ester (b2);
the method for making the polyesteramide resin antistatic, wherein the molar ratio of the hydroxyl groups is in the range of from 0.2 to 0.5;
the method for making the polyesteramide resin antistatic, wherein the chemical compound (c) has at least 3 hydroxyl groups; and
the method for making the polyesteramide resin antistatic, wherein the chemical compound (c) is trimethylolethane, trimethylolpropane or a mixture of trimethylolethane and trimethylolpropane.
In any one of the above methods for making a polyesteramide resin antistatic, it is preferred that either the cyclic amide (a) is xcex5-caprolactam; that the cyclic ester (b1) is xcex5-caprolactone; and that the linear ester (b2) is polycaprolactonediol.
It is preferred that a monomer casting method is used to prepare a polyesteramide resin in any one of the above-mentioned methods for making the polyesteramide resin antistatic.
The antistatic property in the present invention means that the surface resistivity of a molded resin article, measured according to the Japanese Industrial Standards (JIS) K6911, is smaller than 1013xcexa9 (i.e., an order of 1012xcexa9 or smaller). Especially, in applications in the production of semiconductor-related products, a molded resin article preferably has a surface resistivity of an order of from 106 to 1012xcexa9, more preferably 106 to 1010xcexa9.
Further, the present molded resin article is characterized in that its volume resistivity, measured according to JIS K6911, is less than 1011xcexa9.m, preferably from 104 to 108xcexa9.m. It is usually sufficient that a molded article has the antistatic property only on a surface, so that, in some cases, the article is provided with the antistatic property only on its surface. The present molded resin article, on the other hand, also has a low volume resistivity, and, consequently, has the antistatic property in every part.
In the present invention, the surface or volume resistivity is measured according to JIS K6911 as described above. It should be noted that, in the measurements in the present invention, an electrically conductive rubber or paint as specified in JIS K6911 is not used, but the molded article is directly placed between electrodes of a cell chamber, which results in a higher contact resistance than in the case where the above-mentioned electrically conductive rubber or paint is used. If the measurements were made exactly in the manner specified in JIS K6911, a lower resistivity value would be obtained. The measurements are made at 500 V in accordance with JIS K6911, but the resistivity of the present molded resin article can be measured even at 15 V, and the present molded resin article is characterized in that the resistivity is almost constant even if the applied voltage is varied in a range of from 15 V to 500 V.
Further, in the present invention, the antistatic property is evaluated by a half-value period determined by measuring the charged-voltage decay. The half-value period is the time required for the charged electric voltage to reduce to a half, and is a measure of the diffusion property of static electricity of a molded resin article. The half-value period of a molded article is preferably 2 seconds or shorter for a molded resin article to be viewed as antistatic.
The polyesteramide in the present invention is prepared by copolymerizing (a) a cyclic amide and (b1) a cyclic ester and/or (b2) a linear ester.
Examples of the cyclic amide (a) that can be used in the present invention include xcfx89-lactam of the carbon number of from 4 to 12, including xcex3-butyrolactam, xcex5-caprolactam, xcfx89-enantholactam, xcfx89-caprylolactam, and xcfx89-laurolactam. Especially preferred is xcex5-caprolactam. These cyclic amides can be used individually or as a mixture of two or more of them.
Examples of the cyclic ester (b1) that can used in the present invention include xcfx89-lactone of the carbon number of from 3 to 12, xcex2-propiolactone, xcex2-butyrolactone, xcex2-valerolactone, xcex4-valerolactone, xcex2-methyl-xcex4-valerolactone, xcex4-caprolactone, xcex5-caprolactone, xcex1-methyl-xcex5-caprolactone, xcfx89-enantholactone, xcfx89-caprylolactone, and xcfx89-laurolactone. Especially preferred is xcex5-caprolactone. These cyclic esters can be used individually or as a mixture of two or more of them.
The linear ester (b2) is at least one selected from the group consisting of polyesterpolyol, polyesteretherpolyol, and polycarbonatepolyol.
Examples of the polyesterpolyol include those prepared by a dehydration condensation reaction of an aliphatic dicarboxylic acid such as succinic acid, adipic acid, sebacic acid, and azelaic acid, aromatic dicarboxylic acid such as phthalic acid, terephthalic acid, isophthalic acid, and naphthalene dicarboxylic acid, and alicyclic dicarboxylic acid such as hexahydrophthalic acid, hexahydroterephthalic acid and hexahydroisophthalic acid, or esters thereof, or acid anhydrides thereof, with ethyleneglycol, 1,3-propyleneglycol, 1,2-propyleneglycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentylglycol, 1,8-octanediol, 1,9-nonanediol, or a mixture thereof; and polylactonediol prepared by ring-opening copolymerization of a lactone monomer such as xcex5-caprolactone. Among them, polycaprolactonediol is preferably used, particularly polycaprolactonediol having a molecular weight of from about 500 to 2,000.
Examples of the polycarbonatepolyol include those prepared by reacting at least one polyhydric alcohol such as ethyleneglycol, 1,3-propyleneglycol, 1,2-propyleneglycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentylglycol, 1,8-octanediol, 1,9-nonanediol, and diethyleneglycol, with diethylene carbonate, dimethyl carbonate, diethyl carbonate or the like.
Examples of the polyesteretherpolyol include those prepared by a dehydration condensation reaction of an aliphatic dicarboxylic acid such as succinic acid, adipic acid, sebacic acid, and azelaic acid, aromatic dicarboxylic acid such as phthalic acid, terephthalic acid, isophthalic acid, and naphthalene dicarboxylic acid, and alicyclic dicarboxylic acid such as hexahydrophthalic acid, hexahydroterephthalic acid and hexahydroisophthalic acid, or esters thereof, or acid anhydrides thereof, with a glycol, such as diethyleneglycol, and propylene oxide adducts or a mixture thereof. These linear esters can be used individually or as a mixture of two or more of them.
Hereinafter, unless otherwise specified, the amount of each of the above-described ester is expressed as a weight ratio of the ester per 100 weight units of the cyclic amide (a) in total. The weight ratio of the cyclic ester (b1) is in a range of from 3 to 44, preferably from 10 to 34. If the amount of the cyclic ester is less than the above-described lower limit, the required amount of additional electrically conductive material is so large that the disadvantages of conventional technologies emerge. When the weight ratio of the cyclic ester is in the range of from 3 to less than 10, an electrically conductive material such as graphite and carbon black is added or applied on the surface to attain the desired surface resistivity. In that case, a resistivity less than 1013xcexa9 can be attained by adding the conductive material, usually, in an amount of 10 wt %, preferably less than 5 wt %, relative to a molded article, which amount of the addition is significantly smaller than the conventionally required amount. When the weight ratio of the cyclic ester is 10 or more, the desired resistivity is immediately attained without adding an electrically conductive material. Even if the amount of the cyclic ester is larger than the above-mentioned upper limit, there is no problem with the antistatic property, but, in some cases, the mechanical strength or the heat resistance of the molded resin article decreases significantly, or fine bubbles are contained in the molded article, so that the molded article cannot be used as a structural material. Consequently, the weight ratio of the cyclic ester is preferably in the range of from 10 to 34, particularly from 19 to 34. When xcex5-caprolactone is used as the cyclic ester in a weight ratio in the range of from 19 to 24, the surface resistivity is 1010xcexa9; and in the range of 24 or higher, the surface resistivity is constant at 109xcexa9, irrespective of the weight ratio.
The amount of the linear ester (b2), expressed in the weight ratio per 100 weight units of the cyclic amide (a), is in the range of from 2 to 50, preferably from 5 to 45, more preferably from 10 to 40. If the amount of the linear ester is less than the above-described lower limit, the required amount of additional electrically conductive material is so large that the disadvantages of conventional technologies emerge. When the weight ratio is in the range of from 2 to less than 5, an electrically conductive material such as graphite and carbon black is added or applied on the surface to attain the desired surface resistivity, but an amount of less than 10 wt % relative to the molded article is usually enough. When the weight ratio is 5 or more, the resistivity of less than 1013xcexa9 is immediately attained without adding an electrically conductive material. Even if the amount of the linear ester is larger than the above-mentioned upper limit, there is no problem in the antistatic property, but the same problems as mentioned above concerning the cyclic ester (b1) may occur.
When a mixture of the cyclic ester (b1) and the linear ester (b2) is used, their total amount per 100 weight units of the cyclic amide (a) is in the range of from 2 to 50, preferably from 5 to 45, more preferably from 10 to 40, as in the case of the above-described linear ester (b2) is used. The ratio between the cyclic ester (b1) and the linear ester (b2) is not limited and can be determined at will, based on a releasing property from a mold or a desired tensile strength of a molded article.
The present antistatic molded article comprising a polyesteramide resin preferably has a tensile strength, determined according to ASTM D-638, of 40 MPa or higher, more preferably 55 Mpa or higher, most preferably 70 MPa or higher, so that it may be used as a structural material. In that case, the molded article may be treated by heating at about 170xc2x0 C. for about 3 hours, which method is conventionally practised to remove strain and the like from the material.
The present invention relates also to a polyesteramide resin prepared by reacting 100 parts by weight of (a) a cyclic amide, 5 to 50 parts by weight of (b2) at least one linear ester selected from the group consisting of polyesterpolyol, polyesteretherpolyol, and polycarbonatepolyol, or 5 to 50 parts by weight of a mixture of at least 5 parts by weight of the linear ester (b2) and (b1) a cyclic ester, and (c) a chemical compound having a molecular weight of 200 or smaller and having at least 2 hydroxyl groups. The resin preferably has a number average molecular weight, reduced from polystyrene, of from about 4,000 to about 100,000, more preferably from 5,000 to 50,000, as measured by GPC (SSC-7100 chromatograph, ex. Sensyu Kagaku Co.; column:GPC-3506; detector: a differential refractometer; column temperature: 150xc2x0 C.; eluent: m-cresol; flow rate: 0.5 ml/min). Surprisingly, the polyesteramide resin has a lower surface resistivity than the aforesaid 109 to 1012xcexa9, i.e., a surface resistivity of from 106 to 109xcexa9 and a volume resistivity of from 104 to 107xcexa9.m. In addition, it has a good elastic recovery property, a noise extinction property, and a low-temperature property.
Examples of a chemical compound (c) having a molecular weight of 200 or smaller and having at least 2 hydroxyl groups include ethyleneglycol, 1,3-propyleneglycol, 1,2-propyleneglycol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, neopentylglycol, trimethylolethane, trimethylolpropane, glycerol, and diethyleneglycol. These compounds can be used individually or as a mixture. Preferably, a compound having at least 3 hydroxyl groups is used and particularly trimethylolethane and/or trimethylolpropane is preferably used.
Preferably, the chemical compound (c) is used in the reaction in such an amount that the molar ratio of the hydroxyl groups, defined by the following equation, is in the range of from 0.1 to 1.0, more preferably from 0.2 to 0.5:
the molar ratio of the hydroxyl groups molar amount of the hydroxyl group of (c)/molar amount of the hydroxyl group of (b2).
If the ratio is less than 0.1, the effect of reducing the resistivity is not sufficiently attained. Meanwhile, if the ratio is more than 1, the copolymerization reaction does not proceed sometime.
The molded resin article of the present invention can be prepared by a usual method of anionic polymerization. For example, the molded article conforming to a size of a mold can be obtained in one step by a monomer casting method.
A The temperature for the anionic polymerization is generally between 80 and 200xc2x0 C., preferably between 85 and 185xc2x0 C.
Polymerization catalyst and polymerization co-catalyst may be those which are commonly used for anionic polymerization. Examples of the polymerization catalyst include an alkali metal, an alkali earth metal, and a hydride, an oxide, a hydroxide, a carbonate, an alkylate, an alkoxide, and a Grignard compound of these metals and their reaction products with xcfx89-lactam, more specifically, lithium, sodium, potassium, magnesium, calcium, lithium hydride, sodium hydride, potassium hydride, sodium oxide, potassium oxide, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, methyl sodium, ethyl sodium, methyl potassium, ethyl potassium, sodium methylate, sodium ethylate, potassium methylate, potassium ethylate, methyl magnesium bromide, and ethyl magnesium bromide. These polymerization catalysts can be used individually or as a mixture of two or more of them. The amount to be added is normally in a range of from about 4xc3x9710xe2x88x923 to 3 wt % based on the total weight of the cyclic amide (a) and the cyclic ester (b1) and/or the linear ester (b2).
Examples of the co-catalyst or the reaction initiator include isocyanates, acyllactams, carbamidelactams, isocyanurate derivatives, acid halides, and urea derivatives, more specifically, n-butyl isocyanate, phenyl isocyanate, octyl isocyanate, toluene diisocyanate, isophorone diisocyanate, 1,6-hexamethylene diisocyanate, trimethyl hexamethylene diisocyanate, m-xylene diisocyanate, 4,4xe2x80x2-di phenylmethane diisocyanate, N-acetyl-xcexa9-caprolactam, 1,6-hexamethylenebiscarbamide caprolactam, triaryl isocyanurate, terephthaloyl chloride, and 1,3-diphenylurea. These polymerization co-catalysts can be used individually or as a mixture of two or more of them.
When the cyclic ester (b1) is used as the ester, the amount of the co-catalyst or the reaction initiator to be added is in a range of from 0.01 to 4.0 wt %, based on a total weight of the cyclic amide (a) and the cyclic ester (b1). When the linear ester (b2) is used, diisocyanate such as toluene diisocyanate is preferably used as the co-catalyst. In that case, the amount of the diisocyanate to be added is determined depending on the linear ester (b2), but typically in a range, expressed in the molar ratio of isocyanate groups of the diisocyanate to hydroxyl groups of the ester, of from 0.6/1.0 to 1.2/1.0, in addition to the above-mentioned amount of from 0.01 to 4 wt %.
Besides the cyclic amide and the linear ester, other monomers such as a dicarboxylic acid, a diamine, a diol, and an amino acid, or derivatives thereof may be optionally added in such an amount that the antistatic property of the molded article is not spoiled, in the preparation of the present antistatic polyesteramide resin.
In the present invention, in addition to the above-mentioned substances, additives such as pigments, dyes, reinforcing materials, and antimicrobials can be added as required. Further, electrically conductive fillers and electrically conductive polymers may be added and antistatic agents may be applied by coating.